Pressure-responsive device



April 8, 1947. G. A. GEPFRICH 2,418,508

PRES SURE-RESPONSIVE DEVICE Filed Jan. 30, 1946 2 Sheets-Sheet l 5 l N VEN TUIR. BW C W@ Apri-l 8, 1947. G. A. Gol-:PFRICH 2,418,508

PRES SURE-RESPONSIVE DEVICE Filed Jan. so, 194e 2 sheets-sheet z Z7 Z6 f@ 4 24 54 e /g/f l l Ilnl "hf 35 /3/ 'i WZ. TAB- 2 f4 NTOR. e, Q BY A TTU/PAQ? VS Patented Apr. 8, 1947 PRESSURE-RESPONSIVE DEVICE George A. Goepfrich, Stamford, Conn., assignor to rlhe Allied Control Valve Company, Inc., South Norwalk, Conn., a corporation of Connecticut Application January 30, 1946 Serial No. 644,302

10 Claims.

This invention relates to pressure-responsive devices.

In certain hydraulic systems, electric control circuits are provided for regulating the operation of the system. Such circuits include switches operated in response to dilferent pressure variations in the hydraulic system. Heretofore, it has been the practice to provide a pressure-responsive device individual to each switch.

An object of this invention is a single pressureresponsive device designed selectively to operate two switches at different pressure levels.

A further object is a compact and light-inweight device to operate two switches at different pressure levels.

A device embodying the invention preferably comprises a housing having an aperture extending through one wall and a tubular member communicating with the aperture and including a cylinder of larger area than the aperture. A sleeve piston is slidably mounted in the cylinder and has a portion extending through the aperture with a solid piston slidably mounted in said portion. Resilient means individual to each piston bias the two pistons in the same direction and each piston is provided with a conical surface within the housing for engagement with the operating members of a pair of switches arranged within the housing. The housing is connected to a hydraulic system in 'such manner that the pressure in the system is applied to both pistons. The piston areas and the strength of the resilient means are so related that the sleeve piston operates in response to a much lower pressure level than the pressure level at which the solid piston operates. The two switches are, therefore, operated in sequence.

Other objects, novel features and advantages of this invention will become apparent from the following specification and accompanying drawings, wherein:

Fig. 1 is a plan view of a device embodying the invention;

Fig. 2 is a section on the line 2-2 of Fig. l, and

Fig. 3 is a view similar to Fig. 2 with the parts in operated position.

A casing IU has an integral bottom member II and a removable top member or cover I2 which is held in place on the casing by bolts I3. The bottom member I I is provided with an outwardly facing recess I4 which is closed by a tubular member I5 held in place by bolts I 8. Between the inner end of the member I5 and the bottom of the recess I4 are arranged two spring washers l'I. The member I5 is formed with a cylinder I8 in which is slidably mounted a sleeve piston I 9 having a reduced diameter portion 20, one end of which extends through an aperture in the bottom member II concentric with the recess I4 and the other end of which supports sealing members 2| forming a fluid-tight seal with the inner surface of the cylinder I8. A spring 22 is interposed between the bottom of the recess I4 and the sleeve piston I 9 and biases the same outwardly.

Within the portion 29 is slidably arranged a solid piston 23.having itsl inner end extending through the cover member I2. The piston 23 is provided with a collar 24 against which rests one end of a spring 25, the other end of which engages the bottom of an inwardly facing recess 25 in a plug 2T threaded into the cap I2 and having a bore receiving the piston 23. The spring 2e biases the piston 23 away from the plug 21.

The member i5 has a tapped recess 28 receiving a threaded nipple 29 carried by a pipe 30 adapted to contain fluid under pressure. The pressure of the fluid in the pipe 3l! is applied to the ends of both pistons I9 and 23. The pressure exerted by the spring 22 is much less than the pressure exerted by the spring 25 and the fluid pressure is applied to the piston I9 over a larger area than to the piston 23, so that movement of the piston I9 is eiected by lower pressure than is required to effect movement of the piston 23.

In the casing I0 there are arranged two switches 3l and 32 having actuating plungers 33 and 34. The plunger 33 extends into the path of the conical surface 35 at the inner end of the extension 20 while the plunger 34 extends into the path of movement of the conical surface 36 on the piston 23. Movement of the piston I9 from the position shown in Fig. 2 to the position shown in Fig. 3 causes actuation of the plunger 33 while movement of the piston 23 from the po- 'sition shown in Fig. 2 to the position shown in Fig. 3 causes actuation of the plunger 34. Return of the pistons I9 and 23 to their Fig, 2 positions permits return of the plungers 33 and 34 to their original positions. The switches may be of the self-opening or self-closing type according to the circuits which they are to control.

The piston 23 preferably is composed of two sections to reduce manufacturing costs although it may be made in a single piece. A portion of the piston 23 must be in duid-tight but slidable engagement with the inner surface of the bore in the piston I9. Rather than accurately to machine the entire surface of that portion of the piston 23 which contacts the bore surface, the piston is made in two sections, only the lower of which is machined to the required accuracy for fluid-tight engagement.

The fluid pressure in the pipe 30 is applied through the nipple 29 to the ends of both pistons I9 and 23. By reason of the fact that the spring 22 is weaker than the spring 25 and the area of the piston I9 exceeds that of the piston 23, the piston I9 is actuated at a lower pressure level than is the piston 23. Consequently, upon increase of fluid pressure in the pipe 30, the surface 35 engages the plunger 33 before the surface 36 engages the plunger 34, thereby actuating the switches 3| and 32 in sequence. Upon decrease of fluid pressure in the pipe 35i, the two switches are operated in a reverse sequence.

The spring washers ll serve to prevent a surge in the pressure applied to the piston 23 when the piston I9 reaches its limit of movement as they cushion the piston i9 and bring it slowly to a stop, thus avoiding the abrupt stop which would result and produce the undesired surge were the washers omitted. Also, the spring washers will tend to damp out external surges other than those caused by an abrupt stoppage of the piston I9 and they are so designed that they are not totally deflected until the piston 23 starts to move.

It is of course understood that various modications may be made in the structure above described without in any way departing from the spirit of the invention as dened in the appended claims.

I claim:

1. A device of the character described comprising a housing having an aperture extending through one Wall, a tubular member communieating with said aperture and including a cylinder of larger cross-section than said aperture, a sleeve piston slidably mounted in said cylinder and having a portion extending through said aperture, a solid piston slidably mounted in said portion, resilient means individual to each piston biasing the two pistons in the same direction, and a pair of switches within said housing each having an operating member extending into the path of movement of one piston.

2. A device according to claim 1 in which the resilient means differentially bias said pistons.

3. A device according to claim 1 in which the resilient means are designed to require higher pressure to effect movement of one piston than to eiect movement of the other piston.

4. A device according to claim 1 in which the resilient means are designed to require higher pressure to effect movement of the solid piston than to effect movement of the sleeve piston.

5. A device according to claim 1 characterized by means for limiting the extent of movement of the sleeve piston.

6. A device according to claim 1 characterized by means including a resilient unit for limiting the extent of movement of said sleeve piston.

7. A device of the character described comprising a housing having an aperture extending through one wall, a tubular member communicating with said aperture and including a cylinder of larger cross-section than said aperture, a sleeve piston slidably mounted in said cylinder and having a portion extending through said aperture, a solid piston slidably mounted in said portion, resilient means individual to each piston biasing the two pistons in the same direction, an oblique surface on said solid piston and said sleeve piston portion within said housing, and a pair of switches within said housing each having an operating member extending into the path of movement of one oblique surface.

8. A device according to claim 7 in which said resilient means differentially bias said pistons.

9. A device according to claim 8 characterized by means for limiting the extent of movement of said sleeve piston.

10. A device according to claim '7 characterized by means including a resilient unit for limiting the extent of movement of the sleeve piston.

GEORGE A. GOEPFRICH. 

